/**
 * 1. 单独用一个文件定义
 * 2. 开头加上 _
 * 
 * 
*/
class Cat {
  String? color;
  num? _fishNum;

  Cat(this.color, this._fishNum);

  bark() {
    print('嘤嘤嘤');
    this._catchJerry();
  }

  _catchJerry() {
    print('没吃饱，抓老鼠吃');
  }
}
